It is known that skin conductance of a user is related with the level of arousal of a user. Everything that emotionally touches the user activates the sweat glands in the skin leading to a better conductor path through the skin. For example, in a known lie detector or polygraph, a skin conductance sensor connected to the palm of the hand or to the fingers is used.
Commonly, gel electrodes are used for skin conductance sensors. These gel electrodes offer a high signal level. However, prolonged wearing of gel electrodes causes undesirable side effects, such as a white swelling of the skin caused by hydration.
When the period of measurement is long, the skin conductance sensor needs to be comfortable for the user. In the article “A Wearable Sensor for Unobtrusive, Long-Term Assessment of Electrodermal Activity”, Ming-Zher Poh, Nicholas C. Swenson, and Rosalind W. Picard, IEEE Transactions on Biomedical Engineering, Vol. 57, No. 5 (2010) 1243-1252, a wrist-worn integrated sensor is disclosed. This sensor has Ag/AgCl electrodes, and no conductive gel applied to the electrodes. However, due to the Ag/AgCl material, prolonged wearing of this device causes brown skin coloration due to the injection of silver ions into the skin, which is an undesirable side effect.